1. Field of the Invention
The present invention relates to a cushion pin device for a press, and more particularly, to a cushion pin device for a press that moves up and down a cushion pad on which a blank holder is seated so as to generate blanking holding force on a panel which is press-molded, controls lock holding and move-up of the cushion pad through hydraulic control, and controls a locking position degree.
2. Description of Related Art
In general, an automaker produces an automobile by assembling 20 to 30 thousand parts several times.
In particular, as a first step of an automobile manufacturing process, product panels are produced through various types of press devices and thereafter, transferred to a vehicle body factory and respective parts of product panels are assembled to form a vehicle body in a white body (B.I.W) state.
As such, in order to mold a material panel to the product panel, average four press molding processes are gone through, which are constituted by a draw molding process, a trimming and piercing molding process, a cutting and piercing molding process, and a flanging and piercing molding process, and the draw molding process as a process of firing a material according to product data is a primary process of determining 90% or more of the quality of a panel product.
In a general press device applied to the draw molding process, a lower punch having a bottom shape of the product panel is mounted on a lower bolster and a blank holder is mounted on the bolster outside the lower punch through a cushion pin device.
The conventional cushion pin device applied to the press controls a cushion cylinder connected with a cushion pad and an operating position of the cushion cylinder by controlling hydraulic pressure supplied to the cushion cylinder so as to generate blanking holding force by moving up or down the cushion pad on which a blank holder is seated.
However, in such a conventional press device, hydraulic pressure supplied to the cushion cylinders respectively disposed at both sides of the cushion pin device are maintained to be same to control the operating position of the cushion cylinder, and as a result, locking move-up and lock holding of the cushion pad are performed, but a locking position of the cushion pad cannot be controlled under a condition to produce the press with a logic valve which is just turned on/off by only a single signal, and as a result, it is difficult to cope with both a material and an item of a panel.
Further, the locking position of the logic valve should be controlled by changing an output timing of a locking signal for each item (pressure/cushion stroke) and each SPM (production speed) of the molded panel, and as a result, it is complicated to control the logic valve and when a response speed of the logic valve is changed, a distribution of the locking position of the cushion pad is generated. Therefore, the press is inactivated or a problem occurs in quality of the product panel which is press-molded.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.